1). Field of the Invention
Embodiments of the invention relate to a plasma-based substrate processing apparatus. Embodiments of the invention particularly relate to a collimator holding apparatus, which efficiently and accurately positions a collimator over a substrate to enable the plasma-based substrate processing apparatus to selectively deposit and/or remove material at the bottom of a high aspect ratio openings or trenches and/or protrusion.
2). Discussion of Related Art
Plasma-based substrate processing apparatus, such as a Physical Vapor Deposition (PVD) apparatus, may use a collimator, such as a honeycomb type, positioned over a substrate, to improve the directionality of the plasma impinging upon the substrate. Improved directionality may permit reduction of the voltage bias of the substrate, thus reducing potential detrimental effects on the structures formed on the substrate.
Plasma having directionality may be used to improve deposition of materials onto the bottom of high aspect ratio openings or trenches on the substrate being processed. Plasmas having directionality may increase material depositions on surfaces normal to the plasma direction, while reducing material depositions on surfaces parallel to the plasma direction. In cases of small dimension and high aspect ratio openings or trenches, sufficient plasma directionality is required to prevent excessive material depositions onto the sidewalls of openings or trenches, thus closing the openings or trenches at the top before the bottom has been completely filled. Insufficient plasma directionality may cause undesirable void formations in openings or trenches structures being processed. This may result in devices with degraded performance or even failed devices.
Collimators, in some cases, are precariously clipped and/or clamped onto the shielding in a PVD chamber, such as the deposition ring. This approach makes it difficult to adjust the height of the collimator precisely and reproducibly. Furthermore, it is very difficult to level the collimator parallel over the substrate. In addition, the collimator often may not be well grounded to the chamber, either electrically or thermally, which results in the collimator becoming electrically charged and/or excessively hot. These conditions may result in reduced directionality, damage to the collimator, and process variations with processing time.
In some cases, the installation or removal of a collimator in a PVD apparatus may involves a major redesign of the chamber and/or its parts, often requiring a considerable amount of labor, retooling, and expense. Neither the collimator, nor the height of the collimator over the substrate may easily be changed. Such changes may require significant additional retooling of the apparatus, resulting in reduced process flexibility and throughput, while also increasing costs.
Maintenance of the collimator, particularly in deposition processes, may require the periodic removal and reinstallation of the collimator for cleaning purposes. Collimators may need to be cleaned every 200-300 KW hours when performing 1 micron deposits. Difficulties in removing the collimator result in increased maintenance costs, reduced throughput, and decreased process uniformity.